1. Field of the Invention
The present invention relates in general to a fuel injection system for supplying fuel to an internal combustion engine and in particular to such a system for electronically measuring the amount of effective piston stroke travel in a fuel injector while compressing and displacing fuel in a chamber therein to determine the precise amount of fuel delivered to an engine cylinder by the piston movement.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 AND 1.98
It is well known in the prior art that fuel injection systems for supplying fuel to an internal combustion engine utilize a fluid control valve such as a fuel injector that includes a pumping plunger or piston, a solenoid, and an armature for directly actuating the pumping plunger or piston upon energization of the solenoid. The pumping plunger pressurizes fuel in a chamber and the pressurized fuel is forced through an injection nozzle by the pumping plunger to an engine cylinder. The injection nozzle includes a fuel pressure responsive valve that is opened to allow fuel flow when the pressure of fuel supplied to the nozzle attains a predetermined value.
In such a system, the extent of movement of the piston determines the amount of fuel supplied through the injection nozzle to the combustion chamber.
Most such piston-type pumps have some leakage through the piston/cylinder clearance. This leakage past the piston results in a small amount of piston travel that does not displace fuel and thus does not deliver fuel to the engine and is an error in the measured fuel delivery versus piston movement. Furthermore, this leakage changes as parts wear and can also vary with changes in temperature of the fuel injector or the fuel flowing through it. Small variations in manufacturing tolerances from unit to unit can also lead to errors. Such injectors are disclosed in U.S. Pat. No. 4,329,951 and U.S. Pat. No. 4,355,620.
It would be advantageous to have a fuel injector that operated as an accurate flow meter that would electronically measure the amount of effective piston travel to enable the amount of actual fuel delivered to the cylinder to be known. In such case, the fuel injector would become a fuel measurement system as well as a fuel delivery system and most of its parts would do double duty as it performs both functions.
"Effective" piston travel is defined herein as that distance of piston travel that actually results in a displacement of fuel from the fuel injector to the combustion cylinder.